Motor fuel composition



United States Patent Office 3,240,577 Patented Mar. 15, 1966 Thisinvention relates to a motor fuel composition containing a novelanti-knock additive. More particularly, the invention relates to a motorfuel for spark ignition internal combustion engines containing ahydrocarbyl selenite anti-knock agent.

Present day internal combustion engines have high compression ratios andrequire high octane fuels for satisfactory performance. This places asevere strain on petroleum refiners to produce fuels having thenecessary high octane ratings demanded by these engines. The trend tohigher compression ratios is continuing and it is estimated that motorfuels having octane ratings of the order of 105 and above will berequired in the foreseeable future.

At the present time, premium motor fuels having octane ratings of 97 orabove are generally provided by relying heavily on refining operations,such as fluid catalytic cracking, catalytic reforming, alkylation andisomerization, in conjunction with the use of a conventional antiknockadditive, such as a tetraalkyl lead compound. Frequently, these stepsare not satisfactory to efficiently or economically produce a highoctane motor fuel. As a result, many proposals have been made directedto fuel compositions containing additional additives, such as octaneappreciators and the like, to supplement the antiknock property ofpresent day premium motor fuels. Dialkyl selenides are among thematerials that have been proposed as motor fuel additives. They were notsufficiently effective to be adopted commercially and also possessed anextremely objectionable odor. The hydrocarbyl selenites of the presentinvention are extremely effective anti-knock additives and are free ofobjectionable odors.

The subject invention involves the discovery that a gasoline or motorfuel can be substantially improved with respect to its anti-knockproperty by the addition of 0.01 to 5 volume percent of a hydrocarbylselenite. Hydrocarbyl selenites are true anti-knock agents as eviencedby the fact that they will substantially improve the octane rating of amotor fuel in the absence of any other anti-knock additive.

This invention is characterized by a number of important features. It issurprising that hydrocarbyl selenites are anti-knock agents sincesimilar hydrocarbyl esters of elements from the same subgroup of theperiodic table, namely tellurium and sulfur, either are not readilyprepared or impart a pro-knock effect to motor fuels. Another feature isthat hydrocarbyl selenites impart a substantial anti-knock improvementto both very low and very high octane motor fuels. Still anotherimportant feature is that these compounds impart a substantialadditional anti-knock improvement to leaded motor fuels, i.e., motorfuels previously improved in octane value by the presence of aconventional tetraalkyl lead anti-knock agent.

The hydrocarbyl selenite additives of this invention are represented bythe following formula:

in which R and R each represent a hydrocarbyl radical having from 1 to18 carbon atoms. R and R may each represent an alkyl, aryl, alkaryl,aralkyl or alicyclic hydrocarbyl radical and will generally have from 1to 8 carbon atoms. Primary alkyl hydrocarbyl selenites and, inparticular, primary branched-chain alkyl hydrocarbyl selenites arepreferred with a specific preferred species being diisobutyl selenite.It has been theorized that the greater effectiveness of the primaryalkyl hydrocarbyl selenites is due to the formation during engineoperation of aldehydes, which have an octane appreciator effect on lead,if present, and to the selenium-containing residue formed ondecomposition.

The anti-knock additives of this invention can be prepared by reactingthe corresponding hydrocarbyl alcohol with selenium dioxide according tothe following equation:

For example, two moles of isobutanol are reacted with a mole of seleniumdioxide to produce diisobutyl selenite. This reaction takes placereadily by azeotropic removal of water from a mixture of the alcohol andselenium dioxide. The reaction proceeds at ambient pressures and at thenormal boiling point of the azeotrope being formed. Diisobutyl selenite,isobutyl alcohol and water form an azeotrope consisting of 33% by weightof water which boils at 89.8 C. It should be noted that an excess of thealcohol (over and above the 2 moles necessary for reaction) will berequired for the azeotropic removal of water formed during the reaction.The required excess is 0.5 to 1.0 mole of alcohol per mole of waterremoved.

Typical hydrocarbyl selenites which can be employed in this invention inaddition to diisobutyl selenite include, diisoamyl selenite, dimethylselenite, diethyl selenite, isobutyl propyl selenite, ethyl isopropylselenite, di-2-ethylhexyl selenite, didodecyl selenite (so calleddilauryl), dibenzyl selenite, di-n-propyl selenite, din-butyl selenite,dioctadecyl selenite (so called distearyl), ditolyl selenite and thelike.

The motor fuels of the invention consist of gasoline hydrocarbons and aminor amount sufiicient to impart an improved anti-knock property to thefuel of a hydrocarbyl selenite having the formula set forth above inwhich each hydrocarbyl radical has from 1 to 18 carbon atoms. Generally,the hydrocarbyl selenite will amount to about 0.01 to 5 volume percentof the fuel with amounts between 0.1 and 2.5 volume percent beingpreferred. These fuels will generally contain aromatic and/or olefincomponents in addition to the paraflins ordinarily present in a motorfuel. The aromatic and/or olefin components can constitute as high as100 volume percent of the fuel but usually will amount to between about20 and volume percent. There are no critical requirements with respectto the proportions of the volatile hydrocarbon component types in thefuel.

A valuable feature of this invention is that an organolead anti-knockagent can also be employed jointly with the hydrocarbyl selenite toproduce a motor fuel composition having an unusually high octane rating.The organo-lead additives generally employed for anti-knock purposes inmotor fuels are the tetraalkyl lead compounds. Typical tetraalkyl leadanti-knock compounds are tetra ethyl lead, tetramethyl lead, tetrabutyllead, tetraamyl lead, tetrapropyl lead, mixtures thereof and the like.

The tetraethyl lead mixture commercial available for automotive usecontains an ethylene chloride-ethylene bromide mixture as a scavengerfor removing lead from the combustion chamber in the form of volatilelead halides. This product comprises tetraethyl lead, ethylene chlorideand ethylene bromide, the latter two reagents being present in 1.0theory and 0.5 theory, respectively, theory denoting stoichiometricamount required for reaction with the lead content of the tetraethyllead.

The organo-lead reagent is employed in motor fuel compositions inconcentrations between 0.5 ml. per gal- Ion up to the statutory limit oforgano-lead reagent concentration, which at the present .time is 4 ml.per gallon for automotive fuel. The usual concentration of thetetraethyl lead is between 1 and 3 ml. per gallon in gasoline.

The improvement in motor fuels containing fuels containing a hydrocarbylselenite of the invention was demonstrated by incorporating measuredamounts of diisobutyl selenite in various fuel compositions anddetermining the incremental increase in their R.O.N. (Research OctaneNumber). In these runs, diisobutyl selenite was employed as the soleanti-knock agent, i.e., in the absence of any conventional anti-knockagent. Four fuels representing both high and low octane fuels wereemployed in this test. Test Fuel A was substantially pure isooctanehaving an R.O.N. of 100.0. Test Fuel B was an alkylate fuel boiling from126 F. to 368 F. and having an R.O.N. of 97.5. Test Fuel C was a heavystraight run naphtha having an R.O.N. of 52.0, and Test Fuel D was aplatformate boiling from 130 F. to 394 F. having an R.O.N. of 91.2.Various amounts of diisobutyl selenite were incorporated into thesefuels and the incremental increase in R.O.N. value determined. Theseresults of these tests are tabulated in Table I below.

TABLE I Octane effect of diisobutyl selenite in unleaded fuelsDiisobutyl Selenite, Percent vol.

The improvement in leaded motor fuels, i.e., motor fuels containing 3cc. per gallon of tetraethyl lead fluid, brought about by the additionof a hydrocarbyl selenite was demonstrated by incorporating measuredamounts of diisobutyl selenite into various motor fuels and thendetermining the incremental increase in their R.O.N. values as above.Three leaded fuels having different octane values were employed in thesetests. Test Fuel E was a regular grade gasoline boiling from 104 F. to418 F. and having an R.O.N. value of 94.0. Test Fuel F was a premiumgrade motor fuel boiling from 91 F. to 370 F. and having an R.O.N. of99.4 and Test Fuel G was a super premium grade motor fuel boiling from88 F. to 370 F. and having an R.O.N. of 106.0. The incremental R.O.N.improvement in these leaded fuels brought about by adding diisobutylselenite is shown in Table II below.

TABLE II Octane efiect of diisobutyl selenite in leaded fuels Diisobutylselenite, Percent The data in the table shows the improved antiknockeffect of dimethyl selenite in an unleaded motor fuel. This gasoline,designated Fuel H, boiled in the range of 96 F. to 374 and had a R.O.N.of 94.7.

TABLE III Diisobutyl selenite, Research Percent R.O.N.

vol.

The foregoing data demonstrate the effectiveness of hydrocarbylselenites as true anti-knock agents in a variety of leaded and unleadedmotor fuel compositions. These data also show that motor fuels ofunusually high octane value may be obtained through the use of theadditive of the invention.

We claim:

1. A hydrocarbon fuel in the gasoline boiling range containing aneffective anti-knock amount of a hydrocarbyl selenite having theformula:

Se=O in which R and R each represent a hydrocarbyl radical having from 1to 18 carbon atoms.

2. A fuel according to claim 1 in which said hydrocarbyl seleniteamounts to about 0.01 to 5 volume percent of said fuel.

3. A fuel according to claim 1 in which R and R each represent a primaryalkyl radical having from 1 to 8 carbon atoms.

4. A hydrocarbon fuel in the gasoline boiling range containing aneffective anti-knock amount of diisobutyl selenite.

5. A hydrocarbon fuel in the gasoline boiling range containing aneffective anti-knock amount of dimethyl selenite.

6. A hydrocarbon fuel according to claim 4 in which said diisobutylselenite amounts to 0.1 to 2.5 volume percent.

7. A hydrocarbon fuel according to claim 5 in which said dimethylselenite amounts to 0.1 to 2.5 volume percent.

8. A motor fuel in the gasoline boiling range containing an efiectiveanti-knock amount of a tetraalkyl-lead compound and a hydrocarbylselenite having the formula:

in which R and R each represent a hydrocarbyl radical having from 1 to18 carbon atoms.

9. A motor fuel according to claim 8 in which said organo-lead compoundamounts to 0.5 to 3.0 ml. per gallon and said hydrocarbyl seleniteamounts to 0.01 to 5 volume percent of said fuel.

10. A motor fuel according to claim 8 in which said organo-lead compoundis a tetra-alkyl lead compound.

11. A motor fuel according to claim 10 in which R and R in saidhydrocarbyl selenite each represent a primary alkyl radical having from1 to 8 carbon atoms.

12. A motor fuel according to claim 10 in which said hydrocarbylselenite is diisobutyl selenite.

13. A motor fuel according to claim 10 in which said hydrocarbylselenite is dimethyl selenite.

References Cited by the Examiner UNITED STATES PATENTS 1,575,436 3/1926Midgley 44-76 (Other references on following page) 5 UNITED STATESPATENTS 5/1933 Rosenstein et a1 4476 8/ 1933 Rosenstein et a1 44763/1939 Lyons et a1. 4469 2/1949 Lyons et a1. 4468 FOREIGN PATENTS 6/1924 Denmark.

6 OTHER REFERENCES Organic Chemistry, by Richter, 2nd edition, 1919,page 148.

The Effect of Metallic Vapours on the Ignition of Substances, Journal ofInstitution of Petroleum Technologists, February-December 1927, vol. 13,pages 244- 255.

DANIEL E. WYMAN, Primary Examiner.

8. A MOTOR FUEL IN THE GASOLINE BOILING RANGE CONTAINING AN EFFECTIVEANTI-KNOCK AMOUNT OF A TETRAALKYL-LEAD COMPOUND AND A HYDROCARBYLSELENITE HAVING THE FORMULA: